Aggressive insulin therapy for tight glycemic control has been slow to gain acceptance in the clinical setting. One limitation is the inconvenience and poor subject acceptability of injection therapy, especially in a multiple daily injection regimen. In addition, the traditional dosing of pre-meal Regular insulin, 30 to 45 minutes before eating, to obtain optimal postprandial control is inconvenient. The present study is designed to evaluate pre-meal pulmonary delivery of insulin in subjects with Type 1 diabetes mellitus who are currently being treated with combination insulin therapy. The purpose is to determine: 1) whether glycemic control can be achieved at least as effectively with an insulin regimen involving pre-meal inhaled insulin plus twice-daily injections with NPH as with conventional subcutaneous insulin regimen involving pre-meal regular insulin plus twice daily NPH ; 2) the toleration and safety of inhaled insulin therapy and its effects after 6 months, if any, on measures of pulmonary function.